Fan won’t shut off on a C15 cat

Do you have a check engine light on?

 

Ok, I had a check engine light. Other than a bad wire somewhere, the only other thing I can think of is possibly a problem with your ECM.

 

Here is something I found,

There are many things that can cause an engine fan to stay on all the time. They are also tough to troubleshoot because of this. The most common things that cause this are a blown circuit fuse, relay, or control valve for the fan.

The most important thing to remember when troubleshooting the fan is that the Cat ECM sends power out of pin 11 on the ECM to turn the fan off. It's a fail safe. If the wire fails, the fan will stay on and the engine will not over heat.



I would first recommend checking all fuses and breakers. Then I would remove and apply power to the fan control solenoid and see if the fan will engage and disengage. If it does, I would follow the wires from the control solenoid. They should lead to a relay. You can then check to see if the relay is working properly. If it does not, you may have a bad control solenoid or fan hub itself.

You may also want to check the AC high pressure switch as well. You can disconnect it and use a jumper wire to see if it is making the fan stay on.

 

The solenoid is on the fire wall. And yes if you put power to the solenoid and the fan turned off then your solenoid is working properly.

It sounds like from the information I found and posted, the #11 pin on the ECM sends power to turn off the fan. So the number #11 pin should have power to it. If it does, then it is most likely a wire going out of the ECM. @Goodysnap may have some ideas.

 

Cat engine fan is timer based. When you jumped the AC fan cycle switch did you wait for the fan to turn off? Did the AC fan control switch status change in the ECM when jumped vs open?

What chassis do you have and what switch did you jump?

 

Had this issue back in 08 with a Acert. On the truck I was driving it turned out to be the intake air temp sensor that was faulty and causing the fan to stay on.

 

If you jump the A/C high pressure switch you have to keep it jumped for 3 minutes before the fan kicks off , if that is the problem